Just a WAG on my part, thus why I was wondering what the label said. (You did state "Factory racks of 1/2 moon clips prior to being loaded" in your post and my assumption is they were loaded by a device like the one in my pic.)

The do look to be about the right length for it. Who knows, maybe the halfmoonclips were somehow transferred to a permanent halfmoonclip holding bar on the machine, but I feel it would be far simpler and faster to remove an empty halfmoonclip holder and then shove a fully loaded halfmoonclip holder into the machine for ammo loading.